Evaluation of the Conceptual Flow Model for a Deep Vadose Zone System Using Advanced Tensiometers
Deborah L. McElroy*,a and
Joel M. Hubbellb
a Applied Geosciences Department, Idaho National Engineering and Environmental Laboratory, Bechtel BWXT Idaho, LLC., Idaho Falls, ID 83415
b Geosciences Research Department, Idaho National Engineering and Environmental Laboratory, Bechtel BWXT Idaho, LLC., Idaho Falls, ID 83415

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Fig. 1. Location of the Subsurface Disposal Area (SDA) relative to the Idaho National Engineering and Environmental Laboratory, the Big Lost River, and the spreading areas.
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Fig. 2. West to east trending cross section through the Subsurface Disposal Area.
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Fig. 3. Schematic of advanced tensiometer, showing porous cup, transducer, and outer PVC guide pipe.
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Fig. 4. Locations of wells with tensiometers. Blue highlighted squares indicate steady-state conditions and red highlighted circles indicate long-term drying or wetting trends below depths of 17 m (except nested Well 76-5, represented by tensiometers below 18 m). Transient (red) wells tend to be located along the main eastwest road through the center of the SDA.
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Fig. 5. Long-term drying trends at advanced tensiometer locations above depths of 17 m.
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Fig. 6. Stable moisture contents indicating steady-state conditions in the (a) basalt at or below depth of 17 m, (b) BC sedimentary interbed, and (c) CD sedimentary interbed.
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Fig. 7. Long-term wetting and drying trends below 17 m in the (a) BC sedimentary interbed and basalt and the (b) CD sedimentary interbed.
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Fig. 8. Precipitation at the nearby Central Facilities Area, approximately 8 km northeast of the Radioactive Waste Management Complex, for each water year (OctoberSeptember) since 1993. The historical average annual precipitation is 22.1 cm (Clawson et al., 1989).
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Fig. 9. Slope of elevation head vs. hydraulic head is near one, indicating a unit gradient over the upper 73 m of the unsaturated zone in the subsurface in and around the Subsurface Disposal Area.
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Copyright © 2004 by the Soil Science Society of America.